Bad cat?

[DallasTahoe]

98 Yukon 4wd, keep getting code p0430, says catalyst system below efficiency threshold bank 2. Would that be the catalytic converter? I replaced all the o2 sensors a couple years ago just as basic maintenance. Thoughts?


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[exp500]

We are gonna need more Info... Like what engine, mileage, prior exhaust work....
so the answer is "could be". If it is only throwing codes and runs perfect then try new O2 sensors.

 

[DallasTahoe]

We are gonna need more Info... Like what engine, mileage, prior exhaust work....
so the answer is "could be". If it is only throwing codes and runs perfect then try new O2 sensors.

5.7, single flow master 40. New heads 3 years ago, Doesn’t smoke, runs smooth from idle on up. It’s only throwing p0430, no misfiring, no rotten egg smell. I’ve cleared the code a couple of times, just to see how long it takes to come on. Right around 5 miles or 2 key strokes. If it’s a short trip


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[exp500]

Can you tell by your scantool the voltages? F/R sensors? Usually the rear sensor, but the difference and time is what sets code. Some have had success using an adapter adding about 1/2 in length to the port. Cheap fix.

 

[DallasTahoe]

Can you tell by your scantool the voltages? F/R sensors? Usually the rear sensor, but the difference and time is what sets code. Some have had success using an adapter adding about 1/2 in length to the port. Cheap fix.

I swapped the downstream sensors and now no check engine light, I did notice one of them was shorter than the other, the short one is now on bank two and working fine now [emoji2375]


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[exp500]

Please edit your original post title, add "SOLVED". Thanks.

 

[DallasTahoe]

Please edit your original post title, add "SOLVED". Thanks.

Well I can’t, it came back today, I don’t drive it much, mainly on the weekends. Atleast I can rule out the o2 sensor, I’ll pull the plugs tomorrow and check those


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[exp500]

If it's been a couple years, change Dist cap. United DCR820X or Delco.

 

[DallasTahoe]

Can you tell by your scantool the voltages? F/R sensors? Usually the rear sensor, but the difference and time is what sets code. Some have had success using an adapter adding about 1/2 in length to the port. Cheap fix.

I can’t post a video but when I had it on my scanner the downstream sensors were bouncing up and down, but on the bank 2 downstream it wasnt moving as much as bank 1, keep in mind that’s the sensor that was on bank 1, so I’m thinking it is the cat


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[exp500]

They shouldn't bounce, more like a wave if charted. Replug connectors, Ohm check Sensors, Check wires for wear thru or Pinch spots. Might just be bad O2's. Heater circuit is troublesome, may need to wring out the harness. If cats were gone you likely would have performance issues/missfires.

 

[DallasTahoe]

They shouldn't bounce, more like a wave if charted. Replug connectors, Ohm check Sensors, Check wires for wear thru or Pinch spots. Might just be bad O2's. Heater circuit is troublesome, may need to wring out the harness. If cats were gone you likely would have performance issues/missfires.

I say bounce, they were going up and down, but bank 2 wasn’t moving the same as bank 1, And she’s drinking a lot of gas that’s for sure


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[exp500]

Being thirsty is the biggest indicator, You need a tune up. Once she loses 2 mpg consistantly it's time.
Minimum is new cap. You could monitor live data to determine how far you want to go on tune up. No history, do it all.

 

[east302]

Here is the GM diagnostic table for P0430. I thought it might help but it looks like it was written around a Tech2 (step 5).

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[DallasTahoe]

So finally had time to check it out, had it running and it was rattling, so I tapped on the cats and I could hear something jumping around inside, so definitely bad cats. Now I was going to go with Bosal cats, they got them on rock auto. But I found some through muffler express. They’re cheaper and they give free shipping, but I’ve seen a couple posts about bosal being better than most other brands, anyone know anything?


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[BG1988]

98 Yukon 4wd, keep getting code p0430, says catalyst system below efficiency threshold bank 2. Would that be the catalytic converter? I replaced all the o2 sensors a couple years ago just as basic maintenance. Thoughts?


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it's not the CAT you need to have P0420 and P0430 code (4 codes) I had both these codes on and off my self and was able to pass smog without issue.. turned out to be a faulty spark plug and baro for me... the ceramic blew it self apart (the spark plug tip)

if the temp is over 400-700C then they're working ok over that you might be misfiring aka fuel dump or your very high RPM...


check the spark plugs cold engine...


I would check out the MAF sensor this is a typical issue on the older ones i.e GMT800

 

[PatDTN]

I'll toss my experience in here. My cats collapsed completely blocking my exhaust. Right before that I got the same error.

 

[DallasTahoe]

it's not the CAT you need to have P0420 and P0430 code (4 codes) I had both these codes on and off my self and was able to pass smog without issue.. turned out to be a faulty spark plug and baro for me... the ceramic blew it self apart (the spark plug tip)

if the temp is over 400-700C then they're working ok over that you might be misfiring aka fuel dump or your very high RPM...


check the spark plugs cold engine...


I would check out the MAF sensor this is a typical issue on the older ones i.e GMT800

The cats are bad, I can hear stuff moving around on the inside when I tap on them


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[BG1988]

The cats are bad, I can hear stuff moving around on the inside when I tap on them


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what is the temperature?

if you really think it is the CAT

check out the
Aftermarket Catalytic Converter Database It will tell you which ones that work perfect for your SUV...


I suggest a "Walker" cat that is what i used on my old car . and it worked perfect as well had it for 4 years tell i sold it.. Don't let them steal your old cats though you can get a lot of money on ebay for them...